The microsystems are, for example, MEMS (micro-electromechanical systems). These microsystems differ from the macroscopic mechanical systems also by their fabrication method. These microsystems are produced by using the same collective fabrication methods as those used to produce microelectronic chips. For example, the microsystems are produced from slices of monocrystalline silicon or glass machined by photolithography and etching (for example by DRIE (Deep Reactive Ion Etching)) and/or structured by epitaxial growth and the deposition of metallic material.
With these fabrication methods, the microsystems are small and generally have machined pieces or parts of pieces with at least one dimension that is of micrometric magnitude. The micrometric dimension is generally less than 200 μm and, for example, between 1 and 200 μm.
For example, I'ONERA has developed microturbines to convert a fluidic flow into mechanical displacement. Another microsystem for producing the same function is, for example, disclosed in the application WO 03 056 691 or in the application WO 2006/095039.
The microsystems disclosed are capable of converting a pressure difference into a mechanical displacement. However, they present a certain number of drawbacks.
Some of these microsystems require a piece mounted with rotation, generally called rotor. The rotor rotates relative to another immobile piece, generally called stator. The rotor is, for example, a microturbine. Such a rotational movement of the rotor results in friction losses which can be significant, which reduces the energy efficiency of the microsystem. Energy efficiency should be understood to mean the ratio between the mechanical energy produced and the energy supplied to the microsystem in the form of a fluid flow rate or of a pressure difference.
Also, producing a microsystem equipped with a rotating part is complex and often requires numerous semiconductor wafers to be stacked in order to manage to fabricate it.
Finally, the known microsystems achieve a good energy efficiency only for high fluid flow rates. By contrast, for low or very low fluid flow rates, the efficiency is degraded.
Prior art is also known from:    U.S. Pat. No. 5,932,940A,    U.S. Pat. No. 6,368,065B1,    U.S.2004 126254A1,    U.S.2006/057004A1,    WO9641080A1,    U.S.2006/010871A1.